Heavy metals

Question 1

What did we do in this practical?

Answer 1

The concentration of cadmium and lead in canned food samples A and B will be determined and compared against the limits set up by FDA.
We made a lead and a cadmium standard curve using data provided.
Lead uses 405.78 AAS and Cadmium uses 228.802 AAS.
The intensity is plotted against the concentration (ppm)
We blended the contents in 4 samples cans and took out a little of the content and put them in HCl and water. It is heated to a boil and then filtered using a falcon tube. The tube is then handed over for analysis using atomic absorption spectrophotometer.

Question 2

What are heavy metals?

Answer 2

Refers to a group of metals that have relatively high densities or high atomic numbers.
They can toxic or poisonous to humans at low concentrations.
They are non-biodegradable and can accumulate inside humans who consume a food chain accumulating heavy metals.

Question 3

List 2 sources of heavy metals in food

Answer 3

Eating crops grown in soils contaminated with heavy metals

Eating fishes that have grown in waters contaminated with heavy metals

Question 4

Explain how bioaccumulation is related with the intake of heavy metals.

Answer 4

Heavy metals are non-chemically degradable and non-biodegradable.
Heavy metal bioaccumulation begins in the bottom of the food chain where fishes and crops absorb heavy metals from their environment into their bodies. Some species do not have the ability to excrete these heavy metals whereas some species absorb more heavy metals than they excrete. The heavy metals is then transferred up the food chain as the higher trophic levels consume them, resulting in a high bioaccumulation where the human consumes them at the top of the food chain.

Question 5

Calculate the amount of heavy metals in the food using standard curve

Answer 5

1. Obtain a y=mx+c formula from standard curve
2. Calculate the value of x (concentration in ppm) by inserting the y (intensity)
3. Hence, we obtain the concentration. To obtain the total amount in weight, multiply concentration with the weight of the can

Question 6

Compare to the standards by FDA, how much per day?

Answer 6

Lead intakes for

adults 90 μg/day in Belgium, 24 μg/day in Sweden and 177 μg/day in Mexico

Question 7

How to convert ppm to molarity

Answer 7

Ppm is expressed in mg/L

Ppm = (Molarity mol/L * Molar mass) g/L * 1000 = mg/L